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Cyclic normal load–displacement behaviour of clay-coated sand grain contacts
Géotechnique ( IF 5.8 ) Pub Date : 2021-01-06 , DOI: 10.1680/jgeot.18.p.216
Sarvadevabhatla Sathwik KASYAP 1 , KOSTAS SENETAKIS 1 , JIDONG ZHAO 2
Affiliation  

A micromechanical experimental study is presented in this paper investigating the normal contact response of quartz sand grains under cyclic loading. Sand grains with clean surfaces, termed uncoated, and grains coated with commercially available kaolinite powder were studied. The grain contacts were subjected to ten cycles of normal loading within a range from 0 to 5 N. It was observed that uncoated sand grains showed dominantly elastic behaviour, but coated particles had a gradual transition into elastic behaviour after significant plastic deformations in the initial cycles. The normal contact stiffness of coated particles initially increased notably with the number of cycles and reached a maximum value, but uncoated particles showed no variation of normal stiffness against the loading cycles. Similar trends were observed for the stiffness ratio against the loading cycles. Total work input required to reach a given maximum normal load along with elastic and plastic fractions of work input were calculated for coated particles. For uncoated particles, these values were negligibly low, and it was impractical to find elastic and plastic fractions precisely. For coated particles, with a lower preloading at 2 N, the normal load–displacement curve reaching 5 N deviated after a threshold value of 2 N was reached – that is after reaching the previous maximum load the grains contact had experienced. This effect was more pronounced with the increase of the cycles during preloading at 2 N. However, a preloading at 10 N – that is the grains were subjected to greater previous load prior to the normal load–displacement test at 5 N, caused a decrease in plastic deformations and increase in stiffness ratio in the subsequent cycle at 5 N. Uncoated grain contacts did not demonstrate notable variations under the preloading conditions.

中文翻译:

黏土砂粒接触的循环法向荷载-位移特性

本文进行了微机械实验研究,以研究循环载荷下石英砂粒的正常接触响应。研究了具有干净表面(称为未涂层)的砂粒和被市售高岭石粉涂层的砂粒。晶粒接触经历了从0到5 N范围内的十次正常载荷循环。观察到未包覆的砂粒表现出显着的弹性行为,但包覆的颗粒在初始循环中发生明显的塑性变形后逐渐转变为弹性行为。 。涂覆颗粒的法向接触刚度最初随着循环次数的增加而显着增加,并达到最大值,但未涂覆颗粒的法向刚度相对于加载循环没有变化。刚度比相对于加载周期观察到相似的趋势。对于涂层颗粒,计算了达到给定最大法向载荷所需的总功输入以及功输入的弹性和塑性部分。对于未涂覆的颗粒,这些值可以忽略不计,并且精确地找到弹性和塑性部分是不切实际的。对于涂层颗粒,预载荷较低,为2 N,在达到2 N的阈值后,即达到谷物接触之前的最大载荷后,正常载荷-位移曲线达到5 N,这偏离了曲线。在2 N的预加载过程中,随着循环次数的增加,这种影响更加明显。但是,在10 N的预加载–即谷物在5 N的正常载荷-位移试验之前要承受更大的先前载荷,
更新日期:2021-02-16
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